visionmedia / debug / 248 / 1

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master: 89%

Pull #544

travis-ci

introduce `debug.unique()`

When debugging the applications that work with pools of streams
or sockets, the debug stream often comes out interleaved making it
impossible to distinguish between streams. It is a common knowledge
that unique ids could be assigned to each stream and be used in
logging to solve this. However, this solution is rather ad-hoc and
usually applied only during manual debugging.

Introduce `debug.unique([ format ])` method that returns function with
the same signature as `debug`. This function however prepends either
`'%d '` or `format + ' '` (depending on the presence of `format`) to the
first argument of original `debug` function, and supplies unique
integer as a second argument, shifting the rest to the right.

Example:

```
const debug = require('debug')('ns');

class Instance {
  constructor() {
    this.debug = debug.unique('id=%d ');
  }

  method() {
    this.debug('method data=%j', {});
    // "id=123 method data={}"
  }

  attach(other) {
    this.debug('attach to=%d', other.debug.id());
    // "id=123 attach to=456"
  }
}
```

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